Products in the form of aerated dispersions (e.g. gas-in-solution dispersions) are known, such as, for example, foams such as mousse products for styling the hair, as well as whipped cream and other food products that are dispensible from an aerosol can. Such products, however, are known to have poor stability, in particular at room temperature. For example, as can be seen in FIG. 1, an aerated dispersion can evolve over time, with gas bubbles growing and causing the dispersion to degrade.
Past attempts to formulate stable products have had the drawback that the product is affected by the addition of surfactants, polymers, and changes in temperature and/or pH. Other past methods for preparing and stabilizing formulated products utilize components that are toxic and/or produce by-products that can present health hazards and/or introduce prohibitive cost constraints to remove or neutralize them. Additionally, some aerated products are proposed in aerosol cans that simultaneously inject gas and solution, or that must be prepared and kept under frozen conditions to remain stable.
Further problems with the current methods for generating aerated products with particles at the gas-solution interface is that they concern foams and not gas-phase dispersions—that is, the systems have gas-phase volume fractions greater than 64%. In these systems the individual bubbles touch and stick together which makes it difficult to subsequently re-disperse the gas bubble into solution. Furthermore, only hydrophobic particles can be used to achieve even moderate stability.
US 2009/0325780 discloses stabilization of foams and emulsions using partially lyophobic and lyophilized particles. However, it is required to combine the particles in solution with amphiphilic molecules in order to make them hydrophobic before preparing the foam or emulsion. The resulting interfacial adhesion of particles to the surface of the gas bubble, however, is discrete, and somewhat discontinuous, as seen in FIGS. 2 and 3.
In addition to avoiding the above-mentioned drawbacks, there is also a desire in certain industries, such as, for example, the food, cosmetic, and consumer chemical (e.g. household product) industries, to prepare products that have certain properties, such as the ability to be further diluted, for instance.
Thus, there remains a need for methods to prepare gas-in-solution dispersions that provide the desired properties and which can be used in a variety of applications and industries, while providing increased stability of the dispersion and the formulated product.